We will continue our studies with animal cells of 1) Gluconeogenesis and Futile Cycling and 2) of Hepatic Lipogenesis. We will in rat hepatocytes compare the method to measure cycling between fructose 6-P (F6P) and fructose 1,6-P (FDP) by: a) the detritiation of 3-3H and 5-3H glucose and the specific activity of F6P and FDP formed from these sugars with b) a method based on the randomization of galactose 1-14C in the above esters. Methods for the isolation of these esters from rat hepatocytes will be developed. We will measure cycling between PEP and pyruvate from either: a) detritiation of 3-3H lactate in the presence of cycloserine, and b) from the incorporation of NaH14CO into lactate and glucose. The effect of diet, redox state of the cell, and glucagon and epinephrine on the rates of phosphofructokinase and pyruvate kinase during gluconeogenesis and of cycyling will be determined. We will investigate whether there are any futile cycles in intestinal mucosa and in muscle. With hepatocytes from fasted-refed rats we will study the incorporation of 3HOH, glycogen, and specifically labeled glucose, fructose and lactate into fatty acids. A balance of carbon and hydrogen will be determined. The effect of hepatocytes on the incorporation of the above compounds will be determined. The oxidation of glucose 6-P via the pentose cycyle will be determined in rat hepatocytes by several methods. The contribution of the pentose cycle to TPNH production for the reductive synthesis of fatty acids will be determined. The role of malic enzyme and pyruvate cycling in lipogenesis will be studied by use of specific inhibitors.